Tools, containers, or devices for dispensing viscous liquid or semi-liquid products or materials are common and. widespread, and find use in many applications, both commercial (end consumer) and industrial. Such product dispensing tools or containers ideally allow the product to be applied in an accurate, mess-free, and waste-free manner.
Conventional small-volume dispensing packages for viscous liquids such as glues, sealants, greases and the like are frequently either disposable syringes or small cartridges. Common sizes range from 10 ml to 80 ml. The syringe-type dispensers commonly use a hand plunger to expel the material contained in a tube through a dispensing outlet or nozzle. Once all the material is dispensed, the entire syringe dispenser is simply thrown away.
In some cases, mechanical hand dispensers are used. In the past, these manual dispensers have been metal or metal/plastic and have incorporated numerous components, such as springs, levers and guides. Such mechanical dispensers are typically designed to be used in conjunction with sealed cartridges containing the product to be dispensed (sealing caulk, adhesive, lubricant, etc.) The cartridges are typically tubes having a sealed dispensing outlet (a conical tip for example) disposed on one end, with the other end being open for receiving a plunger mechanism or the like from the dispenser. Just inside the cartridge's open end is a slidably-sealed, axially-movable piston, disc, or the like. For use, the cartridge is placed in a retaining/dispensing section of the dispensing device, and the plunger is brought into contact with the piston. When a user desires to dispense product, the cartridge's dispensing outlet is unsealed (typically the closed tip of the dispensing outlet is cut off), and the plunger is forced against the piston through whatever actuation mechanism is employed by the dispenser (frequently a trigger/spring/rod mechanism.) This forces the piston axially down the tube and against the product, which in turn is dispensed through the dispensing outlet.
One such dispensing device is found in U.S. Pat. No. 4,509,662, which discloses a caulking gun.
Although the above disclosed caulking gun and similar dispensing devices are still frequently used, they are disadvantageous in many respects. For example, as mentioned above, they contain many separate moving and non-moving parts, and are therefore relatively difficult and expensive to manufacture and assemble. Also, with many designs, even after the desired amount of product is dispensed the plunger mechanism may still exert force against the cartridge piston, thus causing drooling (that is, further unwanted product to be expelled through the dispensing outlet.) This frequently results in wasted product, and may also result in a substantial mess if the user does not anticipate the additional dispensed product.